In recent years, organic semiconducting (OSC) materials have been developed in order to produce more versatile, lower cost electronic devices. Such materials find application in a wide range of devices or apparatus, including organic field effect transistors (OFETs), organic light emitting diodes (OLEDs), photodetectors, photovoltaic (PV) cells, sensors, memory elements and logic circuits to name just a few. The organic semiconducting materials are typically present in the electronic device in the form of a thin layer, for example of between 50 and 300 nm thickness.
The performance of OFET devices is principally based upon the charge carrier mobility of the semiconducting material and the current on/off ratio, so the ideal semiconductor should have a low conductivity in the off state, combined with high charge carrier mobility (>1×10−3 cm2 V−1 s−1). In addition, it is important that the semiconducting material is stable to oxidation, i.e. it has a high ionisation potential, as oxidation leads to reduced device performance. Further requirements for the semiconducting material are good processability, especially for large-scale production of thin layers and desired patterns, and high stability, film uniformity and integrity of the organic semiconductor layer.
Promising compounds have been disclosed in for example S. Setayesh et al., Macromolecules, 2000, 33, 2016; W. Zhang et al., J. Am. Chem. Soc., 2010, 132(33), 11437; Y.-J. Cheng et al., Chem. Asian J., 2012, 7, 818; H. Bronstein et al, Macromol. Rapid Commun., 2011, 32, 1664; 2: Y.-J. Cheng et al, Chem. Commun., 2012, 48, 3203; WO 2012/058209; US 2012/283377; and B. C. Schroeder, Chem. Commun., 2012, 48, 7699.
In prior art, various materials have been proposed for use as OSCs in OFETs, including small molecules like for example pentacene, and polymers like for example polyhexylthiophene. However, the materials and devices investigated so far still have several drawbacks, and their properties, especially the processability, charge-carrier mobility, on/off ratio and stability do still leave room for further improvement.
One aim of the present invention is to provide new organic semiconducting materials for use in electronic devices, which have advantageous properties, in particular good processability, high charge-carrier mobility, high on/off ratio, high oxidative stability and long lifetime in electronic devices. Another aim is to extend the pool of semiconducting materials available to the expert. Other aims of the present invention are immediately evident to the expert from the following detailed description.